Catheters of the prior art are generally formed of three main elements. A first element is typically the elongated catheter tube. The elongated catheter tube is typically of sufficient length so that the distal end thereof may be positioned near the desired location in a patient while the proximal end thereof remains outside of the patient to allow for the delivery and/or removal of the desired fluids therethrough. A second element of the catheter is generally referred to as a catheter hub. The catheter hub is used to provide for the connection of a fluid delivery or fluid receipt or removal system to the catheter in a manner which is well known in the art. The final element of the catheter is the catheter tip. The catheter tip may be formed of various materials and may have a variety of configurations depending on the intended use of the catheter and the desired position of the catheter tip in the body of the patient.
Strain relief devices have been used in the past to prevent the collapse of a tube when it is subject to lateral (bending) forces. The strain relief device is designed to prevent non-uniform curvature (kinking) of the catheter tube at or near the junction of the hub and catheter tube. Strain relief devices of this type are typically attached to a catheter at a single bonding point or insert molded such that the flexible catheter tube is connected to the more rigid hub at a single stress point. This positioning of the strain relief device prevents bending forces from concentrating at the junction of the hub and catheter tube due to the non-uniform flexibility at the junction. The strain relief device is designed to spread the bending forces along a significant length of the catheter tube and away from the junction of the hub and catheter tube.
Although strain relief devices have previously functioned adequately to relieve the strain of bending forces at the junction of the hub and catheter tube, they have nevertheless been less than adequate to aid in strengthening the junction against axial forces, i.e., forces along the longitudinal axis of the catheter tube which tend to pull the catheter tube away from the hub. Such forces can arise either during normal use, or during any number of common accidents or mishaps. Forces exceeding the strength of the junction of the hub and catheter tube can lead to separation of the hub and catheter tube with disastrous consequences. An example of a strain relief device is disclosed in U.S. Pat. No. 5,330,449 granted to Prichard et al. and assigned to the Assignee of the present invention.
An additional area of a catheter which is prone to kinking or bending forces is the area of the catheter tube which is adjacent to the suture wing. Typically, the suture wing is formed as part of the hub or is located distally along the catheter tube at a location spaced apart from the hub. In the latter situation, the suture wing will be bonded at a single location along the catheter tube and may be a frequent location of catheter kinking when the suture wing is sutured to the skin of the patient. Additionally, when a patient has a suture wing attached to their skin, a common location for kinking is the portion of the catheter tube between the suture wing and the incision site. In this situation, patient movement of their arm, neck or leg may cause axial and longitudinal forces to be applied to the portion of the catheter tube between the suture wing and the incision site depending on the catheter location.
Catheters are routinely manufactured in large quantities and selected catheters are routinely tested for the strength of the bond at the junction of the hub and catheter tube in order to verify that a predetermined minimum allowable pull to separation force is met by the manufactured catheter. For safety reasons, it is critical that the catheters meet the separation forces which routinely occur during normal use of the catheter. Therefore, if a single catheter fails to pass the testing, the entire lot must be scrapped or reworked. Therefore, it is critical that the catheter be manufactured using reliable and consistent components and manufacturing processes.
Therefore, there exists a need in the art to develop a strain relief device which not only functions to relieve strain at the junction of the hub and catheter tube due to bending or torsional forces, but also to relieve strain on the catheter tube due to axial pulling forces, preventing the inadvertent separation of the affected portion of the catheter. Additionally, there exists a need to develop a catheter and manufacturing process in which the catheter consistently meets the minimum pull strength requirements as well as the requirement for a reliable and easily reproducible end product.